In December 2021, Spiniello Companies was awarded Project 2020-424-101-0 from the Pittsburgh Water and Sewer Authority (PWSA). The project — which took place at the Pittsburgh Zoo & Aquarium — consisted of rehabilitating several sewer pipelines in question by using geopolymer lining.
The pipe rehabilitation involved the following line segments, 680 lf of 48-in. sanitary brick sewer, 680 lf of 60-in. sanitary brick sewer, and 150 lf of 101-in. brick arched sewer pipe.
The Geopolymer Solution
Geopolymer has been proven to provide higher compressive and flexural strength than ordinary concrete. With its structural properties, it is a great solution to sanitary sewers, storm sewers, combined interceptors and manholes. There are many advantages of using geopolymer, but primarily it is a cost-effective trenchless solution that provides structural rehabilitation.
This specific project required an overall total of over 450,000 lbs of geopolymer material applied in thicknesses ranging from 1 to 2 in. This internal sprayed-on rehabilitation will extend the life of the pipe more than 50 years and also have saved the owners millions of dollars in excavation and bypass work to expose and replace the pipe. Spiniello crews were able to perform all of the rehabilitation work within the pipe without any excavation.
The Challenge: Safety
With the sewers being more than 70 ft below the ground surface, the Spiniello spray lining crew faced significant safety challenges. Spiniello’s safety director, project management and field operations developed and implemented an extensive site-specific safety plan to ensure everyone involved on the project site was kept safe throughout the project duration.
Spiniello coordinated with the local fire department that was close to the project site to conduct onsite safety briefings to discuss what would be required for a potential rescue scenario. Part of these onsite safety meetings included training on how to properly use specialized winches to reach the depth in which the pipe was located and implementation of a horizontal winch rescue system to ensure the safety of the crew.
Due to the depths associated with the work, communication issues were anticipated between the crew working inside of the pipe and the crew working up top. When required, Spiniello dedicated a man at the base of the manholes to serve as a radio relay between the topside crew and the pipe rehabilitation crew.
The crew mobilized in July 2022 and within a week of mobilizing onsite, started the internal rehabilitation operation at the Pittsburgh Zoo & Aquarium parking lot, which is where the 680 lf of 48-in. sewer line was located, as well as the 680 lf of the 60-in. sewer line. Both sewers were more than 70 vf below the road surface, which provided another challenge for the team, bypassing the sewer.
In normal circumstances, where the pipe invert is no more than 25 ft below the surface, a bypass pump would be set up above ground at the upstream manhole and discharged into the next downstream manhole. Due to the depths of the sewer, this method was not feasible and proved rather costly. The solution would involve an internal bypass of the pipe using hydraulic bypass pumps. This not only allowed the ability to bypass at these excessive depths, but also minimized any traffic disturbances as there was no bypass pipe installed at the surface.
This bypass method was also utilized on the 101-in. sewer. The internal bypass is set up by installing a dam on the upstream side and pumping over the flow with a submersible pump through a discharge hose running directly through the invert of the segment being rehabilitated. This provided a cost savings to the owner, and also limited the work footprint and disturbance above ground.
Despite the challenges, Spiniello completed the project in four months — more than two months ahead of the allotted schedule by PWSA. Spiniello was able to achieve this with experienced crew operations in which higher production was achieved, applying up to 32,000 lbs of material per day and doing it safely in a quality-controlled environment.
The crew operations were monitored daily by PWSA and the engineer of record for the project. This included regular material testing requirements and passing all site safety inspections in which the entire project was completed with no incidents. By the project team opting to incorporate and perform an internal bypass system, Spiniello was able to provide savings to the owner due to no excavation, extensive traffic control.
Tim Bako is vice president, Luis Best is Northeast area manager and Daniel Lee, project coordinator at Spiniello Companies.